Alkali-Metal-Templated Self-Assembly of Nickel(II) [12-MC-3] Metallacoronates Based on Bis(pyrazol-1-yl)acetato Ligands

The syntheses and structures of four new bis(pyrazol-1-yl)acetate- or bis(3,5-dimethylpyrazol-1-yl)acetate-based bis-ligand nickel(II) complexes [Ni(bdmpzmp)(2)] (1), [Ni(bdmpzpen)(2)] (2), [Ni(bdmpza)(2)] (3), and [Ni(bpza)(2)] (4) are described. The results of single crystal structure determinations reveal for all four complexes (3)-coordination of the scorpionate ligands. The sterically hindered bis(3,5-di-tert-butyl-pyrazol-1-yl)acetateto (bdtbpza) ligand allows the synthesis of the nickel(II) chlorido complex [Ni(bdtbpza)Cl] (5). Furthermore, controlled formation of a novel trinuclear linear complex [Ni(bdmpza)(2){Ni(acac)(bdmpza)}(2)] (6) [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] by a self-assembling reaction and alkali metal-mediated template syntheses of [Na{Ni(acac)(bdmpza)}(3)]NO3 (7), [Na{Ni(acac)(bdmpza)}(3)]I (8) and [Li{Ni(acac)(bdmpza)}(3)]NO3 (9) are reported. ESI MS allowed a detailed characterization in solution and is supported by X-ray structure analysis. Compounds 7, 8 and 9 exhibit [12-MC-3] metallacrown structures with a sixfold coordinated alkali metal ion in the center. The magnetic properties are studied by SQUID. Crystallographic data reveal broken symmetry in the solid state for all three [12-MC-3] metallacoronates 7, 8 and 9. The linear structure of [Ni(bdmpza)(2){Ni(acac)(bdmpza)}(2)] (6) (length approximate to 2 nm) obtained through synthesis without template, as well as the molecular structure of the [12-MC-3] metallacoronates 7, 8 and 9 (empty set approximate to 1.3 nm) are at the nanoscale.